(1) Field of the Invention
This invention relates to a coated plastic article having a good appearance without lack of level-dyeing and excellent surface properties such as high-hardness and anti-fogging property.
(2) Description of the Prior Art
Polymers of diethylene glycol bisallyl carbonate are thermosetting plastics utilized in various fields.
Recently, these polymers have been popularly utilized for lenses, especially for sunglasses or ophthalmic lenses, since they are excellent in their optical quality, heat resistance, durability, chemical resistance, impact resistance, dyeability and the like.
These polymers are generally produced by cast-polymerizing a composition containing diethylene glycol bisallyl carbonate in the presence of a peroxide as the radical initiator, for example benzoyl peroxide or diisopropyl peroxydicarbonate.
Shaped articles comprising these polymers are, however, readily scratched during practical application thereof due to low surface hardness. Further, their surfaces easily wet with dew and become opaque under conditions of high temperature and high humidity due to an inferior anti-fogging property, although the polymers have the excellent properties mentioned above.
In order to remove these defects, various improvements have been proposed in which the surfaces of shaped articles of these polymers are coated with materials having a high hardness or good anti-fogging property. For example, a coating material having a high surface hardness is disclosed in U.S. Pat. No. 3,986,997, and an anti-fogging coating is disclosed in U.S. Pat. No. 4,127,682. The present inventors have also proposed, for example in U.S. Pat. No. 4,211,823, a dyeable coating for improving the surface hardness.
However, in the case where a shaped plastic article having an unsmooth portion on the surface thereof is subjected to dyeing, the unsmooth portion is dyed lightly or deeply and said portion is remarkably conspicuous. This defect in the quality of appearance reduced the commercial value of the article remarkably in some uses. Particularly, in articles strictly requiring good optical properties, for example plastic lenses for spectacles, this non-uniform-dyeing is fatal. A lens having two or more different foci, that is the so-called multifocal lens of spectacles for near and distance vision (refer to FIG. 1), and a lenticular lens for cataractous patients (refer to FIG. 2) are hardly used practically due to non-uniform-dyeing in the unsmooth portion (refer to FIGS. 1 and 2, denoted by C) when these lenses are tinted.
In the case of coating a plastic substrate with a certain material, it is known that the wettability and adhesion between the substrate and the coating material are improved by various kinds of surface treatment to the plastic substrate, for example chemical treatment such as alkali-treatment or oxidizing treatment, hot air treatment, flame cleaning, irradiation with ultraviolet or radiation, corona discharge, activation by cold plasma, and the like. These treatments are performed in order to provide the surface of the plastic substrate with polar groups to improve the wettability between the substrate and the coating material.
However, articles made of the polymer produced from diethylene glycol bisallyl carbonate have sufficient adhesion to the conventional coating material, and in usual cases it is not necessary to subject the articles made of the polymer to any of the above treatments. Further, a simple method such as alkali-treatment may be sufficient to improve the adhesion, if necessary.
Nevertheless, in the case where an article made of the polymer has an unsmooth portion on the surface thereof, a remarkably abnormal appearance results due to non-uniform dyeing of said portion when the article is tinted after being coated with a coating material.
U.S. Pat. No. 4,096,315 discloses a process for coating an optical plastic substrate by cold plasma polymerization. However, the substrate is different from diethylene glycol bisallyl carbonate polymer and furthermore the coated article is not dyeable. U.S. Pat. No. 4,137,365 discloses a treatment of a coated plastic substrate with oxygen plasma, and U.S. Pat. No. 4,225,631 discloses a treatment of a coated substrate with ultraviolet or radiation. These treatments, however, are exercised after applying a coating material to a plastic substrate and the non-uniformity of the dyeing is not improved at all. Further, U.S. Pat. No. 4,150,169 discloses a process comprising the steps of prewetting the valleys of an embossed thermoplastic substrate with a liquid of a low viscosity to remove the air bubbles and then coating the substrate with a coating material polymerizable to be a hard polymer by ultraviolet irradiation. Although the process has different objects and advantages from those of the present invention, and non-uniform dyeing is not decreased but instead is promoted by this process.
These disadvantages are overcome by the present invention.
When the polymer is treated with activated gas, ionized radiation and/or active ray according to the invention, the polymer surface, including any unsmooth portions coated with a dyeable coating, can be uniformly tinted.